fix precommit hook not finding mustache version

Due to eslint changes, pre-commit hook was failing to locate version in
mustache.js due to code using single quotes now, therefore "X.X.X" was
not longer matching, and had to be changed to 'X.X.X'.

hooks/pre-commit

@@ -83,7 +83,7 @@ class Bumper
 end
 
 bumper = Bumper.new([
-	Source.new('mustache.js', /mustache.version = "([\d\.]*)"/),
+	Source.new('mustache.js', /mustache.version = '([\d\.]*)'/),
 	Source.new('mustache.js.nuspec', /<version>([\d\.]*)<\/version>/),
 	Source.new('bower.json', /"version": "([\d\.]*)"/)
 ])